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Spark plug photo

Discussion in 'Technical and Troubleshooting Torque' started by typhoon, Aug 11, 2007.

  1. When you ask for help about a problem with your bike, we often want to see a photo of a spark plug.
    This is a good angle:

    We can tell a lot from a spark plug, anyone else want to read this one? It has had something unusual happen to it recently.....

    Regards, Andrew.
  2. Hmm, unique looking ceramic piece. Did it short out internally?
  3. Nope. The spark plug boot stuck to it. Had to break it apart to get the lead off.

    Regards, Andrew.
  4. Looks like an excessive amount of carbon build up.

    But I cant remember if thats due to the engine running too cold or too hot (too hot tends to turn them a more orangey colour?)...I ride and break them, not fix them :p.
  5. O.K some hints. First off, I have already given one, boots stuck to the plug.
    Now, look at the plug gap and the insulator nose, see how it looks shiny? :grin:

    Regards, Andrew.
  6. temperature!
  7. We have a winner! The engine it came from had a severe overheat, the only real clues are the insulator nose is glazed (they are usually a matt, porous finish) the electrode gap has grown massively (overheating lets the side electrode move away from the centre electrode) and the metal above the threaded part of the plug has discoloured oil on it.
    Note that plug colour goes out the window in this sort of situation, depending on teh engine, teh insulator may blister, go yellow/white, or in this case, being a fuel injected engine, just go dark with all teh fuel the ECU dumped into the engine in an attempt to cool things down. This plug had text book light tan colour to the insulator when I pulled it about three weeks ago.

    Regards, Andrew.
  8. Appreciate the write up. How often should sparkies be replaced / checked?

  9. Depends. Some engines "eat" plugs (small block chevs for example) some are kinder to them. Workshop manual is teh best bet, or buy Platinum or Iridium plugs and forget about them for 100k kms!

    Regards, Andrew.